Treatment of dyed textile fabric



Patented D.s,1'942 TREATMENT OF DYED TEXTILE FABRIC Thomas E. Bell,Philadelphia, Pa., assignor to E. I. du Pont de Nemours & Company,Wilmington, Del., a corporation of Delaware No Drawing. ApplicationSeptember 25, 19' Serial No. 412,337

9 Claims.

This invention relates to improvements in the treatment of partiallydyed cotton textile fabrics. More especially, it relates to thestripping of marked-oif dye stains, particularly marked-01f naphthol dyestains, from cotton textile fabrics which have been bleached withalkaline solutions of bleaching agents. In this improved process forstripping marked-off dye stains from these textile fabrics, I employcertain novel oxidizing agents, the organic peracids and persalts.

In the dyeing of cotton textiles, for example with naphthol typedyestuiis, the cloth to be dyed is impregnated with the dyebase, astabilized diazo compound. This dyebase is then developed with aphenolic compound, for example, betanaphthol. As-a result, thereareprobably at least four types of compounds present: fully developeddyestuir; partially developed dyestufi; and unchanged dyebase andunchanged developer. Unchanged dyebase and developer may readily bewashed from the cloth and create no dimculty in the later processing ofthe cloth. Fully developed dyestufis are reasonably resistant to theaction of alkaline oxidizing agents, and mixtures of alkali andoxidizing agents. They therefore cause no difficulty in the subsequentsteps wherein the cotton goods are bleached with alkaline solutions ofoxidizing agent. "However, the remaining product, the partiallydeveloped dyestuff, is less resistant to the action of alkalinesolutions of oxidizing bleaching agents.

In certain bleaching processes wherein alkaline solutions of oxidizingbleaching agents are employed for bleaching cotton textiles containingareas or patterns dyed with naphthol dyestuffs, theconditions underwhich the cloth is handled are conducive to marking-oil of the partiallydeveloped dyestuffs into the white areas of the fabric. Fully developeddyestuffs are apparently not harmed by this treatment, and the patternof the dyestuff is not harmed. In order to strip or remove thismarked-off dyestuff, the stripping should take place in a substantiallyneutral solution when an oxidizing agent is employed, sincedye-stripping treatments involving the'use of alkaline solutions mayresult in additional marking-off of the partially developed naphtholdyestuffs.

In the past it has been customary to strip such marked-01f naphthol dyestains with alkaline solutions of hypochlorites. However, this methodfor removing marked-oft color has not generally given very good resultsbecause the high alka-.

7 linlty of the hypochlorite solutions under some 55 circumstances mightresult in additional marking-ofi of the dye. Moreover, the presence ofthe hypochlorite may result in damage to the textile fabric. Treatmentwith hypochlorites also requires subsequently subjecting the fabric tothe action of an anti-chlor", as well as to several additional washings.For these reasons the hypochlorites, while valuable in strippingmarked-0E color, have not been considered in the industry to be entirelysatisfactory for this purpose.

Unfortunately other common oxidizing agents, such as hydrogen peroxideor alkali metal peroxides, are not efiective in removing marked-01f dyestains. This is true regardless of the pH of the solution of hydrogenperoxide or other inorgan c peroxide applied to the fabric.

i have now found that the organic peracids and persalts are particularlysuitable for stripping marked-off naphthol dye stains from bleachedcotton textiles. Accordingly, it is the primary object of this inventionto develop an improved method wherein these oxidizing agents maycidciently be utilized for the removal or" marked-off dye stains frompartially bleached textile fabrics. In view of the possibility ofadditional marking off occurring if the stripping agent is applied insolutions which are too highly alkaline, it is a further object of thisinvention to develop a method wherein solutions of organic peracids orpersalts which are approximately neutral in reaction are utilized forthis purpose. These and still further objects of my invention willbecome apparent from the ensuing disclosure of certain preferredembodiments thereof.

The oxidizing agents which are utilized for removing marked-off dyesfrom cotton fabrics include the organic peracids and persalts. Theseperacids or persalts may be utilized either as a single percompoound,or, if desired, mixtures thereof may be utilized. The treatment may alsobe applied in one or more stages it necessary, utilizing one or aplurality of these oxidizing agents.

The oxidizing agents utilized may be classified generically as theorganic peracids and products secured by the neutralization, eitherpartial or complete, of these peracids with alkaline agents such ascaustic soda, caustic potash, soda ash, sodium bicarbonate, trisodiumphosphate, ammonium hydroxide, lime, etc. These will include themonoperacids, diperacids, and triperacids, etc., but because of theready availability of the chemical compounds from which they can bepartial or complete, of the peracid solutions with an alkali, I preferto utilize the alkali metal salts, the ammonium, or the alkaline earthmetal salts such as the calcium salts.

Monoperacids constitute a class of acids which ane chemicallycharacterized by the presence of the perhydroxyl grouping -'OOH as partof the molecule. These peracids may be regarded as derived from otheracids by replacing 'the hydroxyl group containing the ionizable hydrogenatom of said acids by the perhydroxyl group OOH. Thus, monopersuccinicacid, one of the acids with which I have had substantial success in theelimination of dye stains from cotton textile fabrics, may be regardedas derived from succinic acid,

cmcoon CHzCOOH Y by the replacement of a hydroxyl group containample,the methods of Bayer and Villiger are described in the Berichte 34, page762 1901) Other methods for preparing these compounds are those of DAnsand his collaborators described in Z. anorg. Chem. 73, page 325 (1912)and in Berichte der Deutschen Chemischen Gesellschaft, vol. 4 5, page1845 (1912). These methods generally involve reacting an acid and aconcentrated solution of a peroxide such as concentrated hydrogen.peroxide.

The percompo'unds and the persalts may also be prepared by reacting anacid anhydride with a dilute or concentrated solution of a peroxide suchI as hydrogen peroxide, or by reacting an acid anhydride with analkaline solution of a peroxide.

In the copending patent application of Reichert;

istics of the solution of the peroxygen compound,

before addition of the acid anhydride, as regards its alkalinity oracidity, are carefully controlled. This method, which utilizesrelatively dilute solutions of peroxides or peroxygen compounds, is onethat I prefer to use, although any method known to the art for producingthe peracids or the salts of the peracids'in solution may be .utilized.

.Any organic peracid or its salt may be utilized as oxidizing agents inmy improved process for stripping marked-off dye stains from cottonfabrics. These peracids may be monoperacids or higher peracids such asdiperacids. Among monoperacidsJor example, the following classes ofacids may be regarded as starting materials for Preparing the peracidsby replacement .of the hydroxyl group containing the ionizable hydrogenatom by the perhydroxyl group OOH: carboxylic organic acids; hydroxyorganic acids; and saturated or unsaturated acids, whether those acidsbe aliphatic or aromatic. Organic acids not characterized by thepresence of-a .carboxyl group, such as sulfonic acids, either aliphaticor aromatic, may also be mentioned. Acids derived fromheterocycliccompounds, such as furoic acid, are included.

Among aliphatic acids from which peracids or their salts may be preparedfor utilization in my process of bleaching may be mentioned monobasicacids, such as acetic acid, and dibasic acids, such as succinic acid.The monoperacids, for example, suitable for use in my process, may beregarded as derived from these aliphatic acids by replacement of thehydroxyl group thereof by th perhydroxyl group. Among hydroxy acidssuitable for use in preparing. peracids which may be utilized inaccordance with my process are acids such as glycolic acid, andunsaturated aliphatic dibasic acids such as maleic acid.

For preparing oxidizing agents suitable for use in my process forremoving marked-01f dyes, by replacement of 'the hydroxyl group'of anacid containing the ionizable hydrogen atom by a perhydroxyl group,there may be mentioned aromatic acids such as benzoic acid, which yieldsmonoperbenzoic acid, a valuable oxidizing agent. Among other aromaticacids may be mentioned monoperphthalic acid, readily derived fromphthalic anhydride. Alicyclic organic acids, such as cyclohexanecarboxylic acid, may also be utilized to prepare peracids and persaltswhich may be efiectively utilized in my process.

Among sulfonic acids from which peracids and their salts capable ofutilization in my process may be prepared are acids such as benzenesulfonic acid. Among'heterocyclic acids, nicotinic and quinolinic acidsform suitable starting materials for preparing peracids suitable for usein treating cotton goods to strip ofi dye stains.

Among the various organic peracids I prefer to use monopersuccinic acidor its salts, monoperphthalic acid or its salts, and peracetic acid orits salts. In view of the relative inexpensiveness and readyavailability of acetic anhydride, from which peracetic acid is prepared,peracetic acid and salts of this acid may be regarded as my pre-- ferredagent.

However, perpropionic acid, perbutyric acid, perc'rotonic acid,monopermaleic acid, monoperglutaric acid, perbenzoic acid,diperterephthalic acid, monoperadipic acid, perglycolic acid(bydroxymonoperacetic acid) and the salts of these acids are among theorganic peracids and their salts which may be utilized in accordancewith my process in the treatment of dyed cotton goods.

The stripping of marked-0E naphthol dye stains may be carried out byeither a steeping or a saturation method. In the steeping method, thedyed cotton cloth to be treated is allowed to soak in an amount ofperacid or persalt solution which is several times the weight of theydry material, this soaking continuing for the duration of the treatment.In the saturation method the cloth is thoroughly wet out in the peracidor persalt solution and excess'solution over. that necessary to moistenthe goods uniformly removed by suitable means. The cloth is then storedin the moistened condition for the duration of the treatment. Whenpracticing the saturation method, it is preferred to saturate the clothat room temperature. The temperature is then raised to the strippingtemperature and Ordinarily it is preferred to utilize solutions oforganic peracids or persalts which have pH values not appreciably inexcess of 8.0. The pH of the solution is readily adjusted by theaddition of alkali or acid, as needed, in order to secure one ofapproximately 8.0. However, this pH is not unduly critical and it may bevaried somewhat over fairly wide limits of acidity a and alkalinity. Forsome industrial purposes it may be desirable to strip the marked-offnaphthol dye stains from the textile fabrics with solutions of lower pHvalues, such as pHs of 6.0 to 7.0. In general, however, in the use ofperacid or persalt solutions for stripping marked-off naphthol dyestains, a pH value in excess of 9.0 is of no particular advantage as thestain strip ping activity of the peracids or persalts decreases rapidlyat pH values above 9.0. The ability of the peracid or persalt to removenaphthol dye stains is greatest in the pH range 7.0 to 9.0 and decreasesonly slightly as the pH decreases. For my purpose, however, I prefer toemploy the organic peracid and persalt solutions for stripping naphtholdye stains from cotton fabrics at a pH of approximately 8.0, in this wayavoiding the danger of marking off additional dyestuffand thus securingadditional staining by the employment of solutions which are tooalkaline.

The condition of the marked-off naphthol dye stain and the procedureelected for carrying out thefstripping will generally control conditionsof time, stripping temperature, and the concentrations of strippingagent utilized in the process. Organic peracid or persalt solutions ofany concentration may be employed, but I prefer to utilize aconcentration ranging from 0.25 volume to 1.0 volume, depending upon theintensity of the marked-off dye stain to be removed. The volumeconcentration of a solution of a percompound is a usual manner ofexpressing its concentration, and is defined as the number of volumes ofoxygen gas, measured at 0 C. and 760 I mm. of mercury pressure, whichwillbe released upon complete decomposition of the percompound from onevolume of the solution maintained at 20 C.

Ordinarily it is preferred to utilize elevated temperatures in theprocess as the use of such temperatures greatly reduces the timerequired satisfactory stain removal has been secured in. the temperaturerange 50 F. to 210 F. If tem,.

peratures above 120 F. are mair'itained,'together with concentrations oft he organic peracidor persalt solution ranging from 0.25 volume to 1.0

volume, the stripping operation will generally be completed in a veryshort period of time, for example, aperiod ranging from one-half to onehour.

As an example of my improved method for stripping marked-off naphtholdye stains from cotton textile fabrics, the following may be given:

Example Cloth batches stained with marked-off paph-.

thol dye stains were immersed in various solutions of peracetic acid ofconcentration ranging from 0.125 volume to 1.0 volume, these solutionsall having a pH of approximately 8.0. Temperatures ranging from F. to160 F. were maintained. In all cases the stains were stripped from thefabric at the end of three hours and, in most cases, especially wheretemperatures of F. or higher were maintained, stain removal was completein one hour or less.

In place of peracetic acid or salts of this per;- acid as utilized inthe above-described illustra tive example, other organic peracids orpersalt may be employed as stripping agents. However, monopersuccinicacid, monoperphthalic acid, and peracetic acid, and their salts arepreferred as stain stripping agents because of the commericalavailability and low cost of the substances'from which solutions ofthese agents may be prepared. But perpropionic, perbutyric, percrotonic,monopermaleic, monoperglutaric, perbenzoic, diperterephthalic, andperfuroic acids, and their salts will, in general, give satisfactoryresults in the removal of marked-off naphthol dyes.

It may be remarked that in no case wherein peracids or their salts havebeen utilized for removing marked-off naphthol dye stains from cottongoods, or from goods consisting largely or predominantly of cotton, hasthere been observed any objectionable degradation or weakening inappears in the textile treating bath, i. e., whether the compound ispresent in the formof the peracid or in the form of a salt of a peracid,depends largely on the pH of the solution and on the alkaline agentsadded to neutralize or partially neutralize the peracid (if in fact anysuch alkaline agents are added) it is apparent that there is noessential difference in my process regardless of whether the peracid orits salt is present. Accordingly, I employ the term peracid as includingboth the acid itself and salts of the acid, such as the various metalperacetates, perphthalates, perbenzoates, etc.

Wherever I refer in the claims to fcottonf cotton goods, or cottontextiles, I mean to include within the scope of 'that term both fabricsconsisting substantially entirely of cotton, as well as those consistinglargely or. predominantly of cotton but containing, in addition,non-cotton fibres. Y

It will be apparent that many changes may be made in my process asherein described which will nevertheless fall within the scope of theinvention. Accordingly, it is my intention that the invention is not tobe restricted to the various de-.

tails, conditions, amounts and procedures given as typical andillustrative of preferred embodiments, except insofar as necessitated bythe prior art and appended claims.

I claim:

1- The mf in ad of treating dyed cotton textile fabrics inorder .toremove marked-off naphthol dye stains therefrom which comprisescontacting said fabric with an aqueous solution of an organic peracid.

2. The method of treating dyed cotton textile fabrics in order to removemarked-01f naphthol dye stains therefrom which comprises subjecting saidtextile fabric to the action of an aqueous solution of an organicperacid having a pH falling within the range 6.0 to 9.0.

3. The method of treating dyed cotton textile fabrics in order to removemarked-off naphthol dye stains therefrom which comprises subjecting saidtextile fabric to the action of an aqueous solution of an organicperacid having a pH of approximately 8.0.

4. The method of treating dyed cotton textile fabrics in order to removemarked-off naphthol dye stains therefrom which comprises subjecting saidtextile fabric to the action of an aqueous solution of an organicperacid at a temperature in excess of 120 F.

5. The method of treating dyed cotton textile fabrics in order to removemarked-off naphthol dye stains therefrom which comprises subjecting saidtextile fabric to the action of an aqueous solution ofan organic peracidhaving a volume concentration ranging from 0.125 volume to 1.0

volume." I

6. The method of treating dyed cotton textile fabrics in order to removemarked-off naphthol dye stains therefrom which comprises subjecting saidtextile fabric to the action of an aqueous solution of, an organicperacid at a temperature in excess of 120 F., said solution having aperacid concentration ranging from 0.25 volume to 1.0 volume.

7. The method of treating dyed cotton textile fabrics in order to removemarked-01f naphthol dye stainstherefrom which comprises subjecting said,textile fabric. to the action of. an aqueous solution of peraoetic acid.

8. The method of treating dyed cotton textile fabrics in order to removemarked-off naphthol dye stains therefrom which comprises subjecting saidtextile fabric to the action of an aqueous solution of monoperphthalicacid.

9. The method of treating dyed cotton textile fabrics in order to removemarked-off naphthol dye stains therefrom which comprises subjecting saidtextile fabric to the action of an aqueous solution of monopersuccinicacid.

THOMAS E. BELL.

